1. Field of the Invention
The present invention relates to a connection device for connecting an optional device to a main body and making an electrical conduction between them. The present invention also relates to an image forming apparatus and an optional device equipped with the connection device.
2. Description of Related Art
Conventionally, a mechanical connection as well as an electrical conduction is realized between an image forming apparatus and an optional device, i.e., a post processor (that performs post processes such as a sorting process, a stapling process and a punching process of delivered paper sheets) in the following way using a conventional connection device. Note that the electrical conduction is necessary for preventing a malfunction or the like of the image forming apparatus due to static electricity charged in the post processor or radiation noises from the post processor. Hereinafter, a copying machine is exemplified as the image forming apparatus for explanation. FIG. 6 is an elevation view showing schematically a post processor that is equipped with a conventional connection device and a copying machine. Furthermore, FIGS. 7A and 7B are longitudinal sections showing schematically the conventional connection device for connecting the post processor to the copying machine. More specifically, FIG. 7A is a longitudinal section showing the conventional connection device before the post processor is connected to the copying machine, and FIG. 7B is a longitudinal section showing the conventional connection device after the post processor is connected to the copying machine. Furthermore, FIGS. 8A and 8B are schematic views from a side of the conventional connection device for explaining a lock mechanism of a positioning pin. More specifically, FIG. 8A is a schematic view from a side of the conventional connection device for explaining an unlock position, and FIG. 8B is a schematic view from a side of the conventional connection device for explaining a lock position. Note that a position where a user operates the copying machine corresponds to a front side of the copying machine.
As shown in FIG. 6, a post processor 70 is equipped with connection devices 71 for fixing positioning pins 51 and making an electrical connection when the post processor 70 is attached to the copying machine 50. Two pairs (total four) of connection devices 71 are disposed on the front and the rear sides of a conductive frame 72 of the post processor 70 as shown in FIG. 6.
As shown in FIG. 6, a copying machine 50 is equipped with conductive positioning pins 51 for making a mechanical connection and an electrical connection to the frame 72 of the post processor 71. Two pairs (total four) of the positioning pins 51 are disposed on the front and the rear sides of a conductive frame 53 of a main body exposed at a paper delivery portion 52 as shown in FIG. 6. Note that each of the frames 53 and 72 is arranged to cover a predetermined area for preventing a malfunction or the like of the image forming apparatus due to static electricity charged in the post processor or radiation noises from the post processor. Hereinafter, the positioning pin 51 and the post processor 71 will be described.
As shown in FIGS. 7A and 7B, the positioning pin 51 is made up of a conductive member having a columnar shape, and an end of the positioning pin 51 is provided with a thread portion 51d for fixing to the frame 53 and making electrical connection with the same. In addition, the positioning pin 51 includes a flange portion 51c, a stopper portion 51a and an engaging portion 51b. The flange portion 51c is fastened to the frame 53 with the thread portion 51d. The stopper portion 51a has a diameter that is the largest and tapered toward the other end for contacting a plate spring 77 described below when the post processor 70 is attached. The engaging portion 51b is closer to the fixed side than the stopper portion 51a and has a reduced diameter smaller than the stopper portion 51a. The positioning pin 51 is screwed to the frame 53, so it has an electrical connection with the frame 53.
As shown in FIGS. 7A through 8B, the conventional connection device 71 includes a conductive fixed locking member 73 and a conductive movable locking member 74. The fixed locking member 73 is fixed to the conductive frame 72 of the post processor 70 with a screw 78, and it has a pin insertion hole 75 having an opening with a diameter larger than the outer diameter of the positioning pin 51 on the frame 53 side of the copying machine 50 and a conductive plate spring 77 that is attached to the inner face of the fixed locking member 73 at the vicinity of the pin insertion hole 75 so as to close the pin insertion hole 75. The movable locking member 74 abuts the outer face of the fixed locking member 73 and is slidable in a sliding direction that is perpendicular to the insertion direction of the positioning pin 51, and it has an elliptic hole 76 extending in the sliding direction for inserting the positioning pin 51.
As shown in FIGS. 8A and 8B, the elliptic hole 76 of the movable locking member 74 includes a large diameter portion 76a and a small diameter portion 76b. The large diameter portion 76a has an opening diameter larger than the outer diameter of the stopper portion 51a of the positioning pin 51 and overlaps the pin insertion hole 75 of the fixed locking member 73 in the unlock position of the movable locking member 74 (the position shown in FIG. 8A) for permitting insertion of the positioning pin 51. The small diameter portion 76b extends from the large diameter portion 76a in the sliding direction for retaining the stopper portion 51a of the positioning pin 51 in the lock position of the movable locking member 74 (the position shown in FIG. 8B) in the state where the positioning pin 51 is inserted. In addition, an opening diameter 76c of the small diameter portion 76b is smaller than maximum outer diameters of the large diameter portion 76a and the stopper portion 51a of the positioning pin 51, and it is larger than the engaging portion 51b of the positioning pin 51.
Next, attachment and detachment of the post processor 70 having the conventional connection device 71 with respect to the copying machine 50 will be described below. Before attaching the post processor 70 to the copying machine 50, the movable locking members 74 of each of the connection devices 71 is moved to slide to the unlock position outward from the post processor 70 in the sliding direction as shown in FIG. 8A. Then, the pin insertion hole 75 of the fixed locking member 73 and the large diameter portion 76a of the movable locking member 74 are overlapped with each other so as to become in the state where the positioning pin 51 can be inserted.
Then, as shown in FIGS. 6 and 7A, the post processor 70 is moved by the user toward the copying machine 50 (in the direction of an arrow A). Then, the positioning pin 51 is inserted in the pin insertion hole 75 and the large diameter portion 76a. Further, the engaging portion 51b of each of the positioning pins 51 is inserted until it reaches the position of the large diameter portion 76a of each of the movable locking members 74.
Next, each of the movable locking members 74 is moved to slide from the unlock position shown in FIG. 8A toward the inside of the post processor 70 (in the direction of an arrow B) to the lock position shown in FIG. 8B. Then, as shown in FIG. 7B and FIG. 8B, the small diameter portion 76b of the movable locking member 74 moves to the engaging portion 51b of the positioning pin 51. Since the opening diameter 76c of the small diameter portion 76b of the movable locking member 74 is smaller than the outer diameter of the stopper portion 51a of the positioning pin 51, the stopper portion 51a is retained in the small diameter portion 76b. As a result, the engaging portion 51b of the positioning pin 51 is engaged with the small diameter portion 76b of the movable locking member 74 so that the positioning pin 51 is fixed by the engagement. On this occasion, the plate spring 77 contacts the stopper portion 51a of the positioning pin 51 so that an electric conduction is formed between them as shown in FIG. 7B. Therefore, the frame 72 of the post processor 70 is connected electrically to the frame 53 of the copying machine 50 via the fixed locking member 73, the movable locking member 74, the plate spring 77 and the positioning pin 11.
Furthermore, JP-A-11-193136 discloses an image forming apparatus that includes a connection device having a structure in which a conductive positioning pin of a paper feed device is engaged with a positioning hole of a main body. When the paper feed device is connected to the main body, a conductive elastic member provided to the main body abuts the positioning pin so that electric connection can be formed between the ground of the main body and the ground of the paper feed device. In addition, a sheet processor (corresponding to a sheet loading device) is connected to a conductive rail that is connected to the paper feed device, so that the sheet processor can be connected to the ground.
It is certainly possible for the conventional connection device 71 described above to fix the positioning pin 51 by the engagement between the engaging portion 51b of the positioning pin 51 and the small diameter portion 76b of the movable locking member 74 in the lock position of the movable locking member 74 when the post processor 70 is attached to the copying machine 50, and to make a electric conduction between the frame 72 of the post processor 70 and the frame 53 of the copying machine 50 when the plate spring 77 that is connected electrically to the frame 72 of the post processor 70 contacts the positioning pin 51.
In addition, it is possible for the image forming apparatus including the connection device disclosed in JP-A-11-193136 to connect the sheet processor to the ground of the image forming apparatus by making the electrical contact between the sheet processor and the conductive rail that is connected to the paper feed device.
However, the conventional connection device 71 has a problem as follows. Although the connection device 71 is required to make an electric conduction between the frame 72 of the post processor 70 and the frame 53 of the copying machine 50, to prevent the post processor 70 from being detached from the copying machine 50 due to a vibration or the like, and to be capable of detaching the post processor 70 from the copying machine 50 easily when a malfunction such as a paper jam, it is difficult to insert the positioning pin 51 or fix the positioning pin 51 by the engagement since a force of the plate spring 77 works in the direction of removing the positioning pin 51 from the connection device 71.
In addition, the image forming apparatus including the connection device disclosed in JP-A-11-193136 has a disadvantage of much effort necessary for detaching the sheet processor from the rail when a malfunction occurs in the sheet processor since the sheet processor (corresponding to the sheet loading device) is connected to the conductive rail that is connected to the paper feed device.